Gene delivery via nanotubes changes fish sex to boost aquaculture yield

Mandarin fish (Siniperca chuatsi) is an economically important fish in China, with the females grow ingfaster than males. Thus, it is critical to obtain neo-male individuals for breeding all-female mandarin fish. This research demonstrates a novel and non-invasive method for inducing sexual reversal in all-female mandarin fish populations, a development with significant potential for aquaculture. By using functionalized Single-Walled Carbon Nanotubes (SWCNTs) as a delivery vehicle, we successfully introduced key sex-determining genes (amh and amhy) into juvenile fish through a simple immersion bath.

In a new study published in Water Biology and Security, a team of researchers in China not only confirmed the critical role of amh and amhy in mandarin fish sex determination but also established functionalized SWCNTs as a promising tool for gene delivery in fish.

"We were surprised by the efficiency of this delivery system," shares lead author Chong Han. "The functionalized nanotubes effectively carried the plasmid DNA across biological barriers, leading to detectable gene expression in the gonads, which is a major hurdle for bath-based methods."

Traditionally, creating "neo-male" (XX male) broodstock for all-female production relies on hormone treatments or invasive plasmid injections, which is labor-intensive and can raise environmental concerns.

A key point of interest was the clear biological outcome: a significant proportion of fish in the high-concentration (40 mg/L) groups developed masculinized gonads. Molecular analysis confirmed the expected shift, with downregulation of female pathway genes (foxl2, cyp19a1a) and upregulation of male genes (amh, dmrt1). Furthermore, our in vitro assays provided a mechanistic insight, showing that the delivered genes activate the male sex-determining pathway via the amhrII/smads signaling cascade.

“Our findings shine a new light on this process by providing a simpler, needle-free alternative,” adds Han. “The technique improved upon existing bath immunization approaches, which are often ineffective, by leveraging the unique cargo-delivery properties of carbon nanomaterials.”

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Contact the author: Zhang yong, Sun yat-sen university, lsszy@mail.sysu.edu.cn

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